Browsing by Author "Eblen-Zajjur, Antonio"

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    Comparison of LED- and LASER-based fNIRS technologies to record the human peri-spinal cord neurovascular response
    (2024) Caulier-Cisterna, Raill; Appelgren-Gonzales, Juan -Pablo; Oyarzun, Juan -Esteban; Valenzuela, Felipe; Sitaram, Ranganatha; Eblen-Zajjur, Antonio; Uribe, Sergio
    Recently, functional Near-Infrared Spectroscopy (fNIRS) was applied to obtain, non-invasively, the human peri-spinal Neuro-Vascular Response (NVR) under a non-noxious electrical stimulation of a peripheral nerve. This method allowed the measurements of changes in the concentration of oxyhemoglobin (O2Hb) and deoxyhemoglobin (HHb) from the peri-spinal vascular network. However, there is a lack of clarity about the potential differences in perispinal NVR recorded by the different fNIRS technologies currently available. In this work, the two main noninvasive fNIRS technologies were compared, i.e., LED and LASER-based. The recording of the human peri-spinal NVR induced by non-noxious electrical stimulation of a peripheral nerve was recorded simultaneously at C7 and T10 vertebral levels. The amplitude, rise time, and full width at half maximum duration of the perispinal NVRs were characterized in healthy volunteers and compared between both systems. The main difference was that the LED-based system shows about one order of magnitude higher values of amplitude than the LASER-based system. No statistical differences were found for rise time and for duration parameters (at thoracic level). The comparison of point-to-point wave patterns did not show significant differences between both systems. In conclusion, the peri-spinal NRV response obtained by different fNIRS technologies was reproducible, and only the amplitude showed differences, probably due to the power of the system which should be considered when assessing the human peri-spinal vascular network.
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    Enoxaparin pretreatment effect on local and systemic inflammation biomarkers in the animal burn model
    (2019) Vicci, Hember; Eblen-Zajjur, Antonio; Lopez, Mercedes; Crespo, Gustavo; Navarro, Maria
    Low-molecular weight heparins (LMWH) are anticoagulants that have shown anti-inflammatory activity in several experimental models. Hot water burn inflammatory model accurately simulates human clinical situations allowing its use for nociception test and evaluation of anti-inflammatory drugs. The present study aims to evaluate the enoxaparin pretreatment on local and systemic inflammation biomarkers in the animal burn model. Inflammation was induced by submersing the rat left hind paw in water at 60(o)C for 60s. C-reactive protein (CRP) and thrombin-antithrombin complex (TAT) were estimated by immunosorbent assay, fibrinogen (Fg) by the gravimetric method and paw oedema by orthogonal digital photography. Highest values of paw oedema, CRP and TAT were observed at 4h post-burn while Fg peak occurs at 12h post-burn; enoxaparin pretreatment decreased oedema (-32.1%), and concentration of TAT (-66.7%), PCR (-37.9%) and Fg (-8%). This study shows that enoxaparin has local and systemic anti-inflammatory effects and should be considered as a potential adjuvant drug for the treatment of burns.
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    Non-Invasive Functional Evaluation of the Human Spinal Cord by Assessing the Peri-Spinal Neurovascular Network With Near Infrared Spectroscopy
    (2021) Valenzuela, Felipe; Rana, Mohit; Sitaram, Ranganatha; Uribe, Sergio; Eblen-Zajjur, Antonio
    Current medical care lacks an effective functional evaluation for the spinal cord. Magnetic resonance imaging and computed tomography mainly provide structural information of the spinal cord, while spinal somatosensory evoked potentials are limited by a low signal to noise ratio. We developed a non-invasive approach based on near-infrared spectroscopy in dual-wavelength (760 and 850 nm for deoxy- or oxyhemoglobin respectively) to record the neurovascular response (NVR) of the peri-spinal vascular network at the 7th cervical and 10th thoracic vertebral levels of the spinal cord, triggered by unilateral median nerve electrical stimulation (square pulse, 5-10 mA, 5 ms, 1 pulse every 4 minutes) at the wrist. Amplitude, rise-time, and duration of NVR were characterized in 20 healthy participants. A single, painless stimulus was able to elicit a high signal-to-noise ratio and multi-segmental NVR (mainly from Oxyhemoglobin) with a fast rise time of 6.18 [4.4-10.4] seconds (median [Percentile 25-75]) followed by a slow decay phase for about 30 seconds toward the baseline. Cervical NVR was earlier and larger than thoracic and no left/right asymmetry was detected. Stimulus intensity/NVR amplitude fitted to a 2nd order function. The characterization and feasibility of the peri-spinal NVR strongly support the potential clinical applications for a functional assessment of spinal cord lesions.
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    Non-invasive near-infrared spectroscopy assessment of the spinal neurovascular response in a patient with transverse myelitis: a case report
    (2022) Oyarzún Isamitt, Juan Esteban; Caulier Cisterna, Raúl; González Appelgren, Juan Pablo; Gonzalez, Leticia; Trujillo, Oscar; Eblen-Zajjur, Antonio; Uribe Arancibia, Sergio A.
    Background: Transverse myelitis (TM) is characterized by acute development of motor, sensory and autonomic dysfunctions due to horizontally diffused inflammation in one or more segments of the spinal cord in the absence of a compressive lesion. The not well-known inflammation process induces demyelination resulting in neurological dysfunction. Case presentation: In this case report we used a functional Near-Infrared Spectroscopy (fNIRS) technique to evaluate changes in the peri-spinal vascular response induced by a peripheral median nerve electrical stimulation in a patient with chronic transverse myelitis (TM). fNIRS showed drastically reduced signal amplitude in the peri-spinal vascular response, compared to that obtained from a healthy control group throughout most of the C7-T1 and T10-L2 spinal cord segments. Conclusion: The potential use of this relatively non-invasive fNIRS technology support the potential clinical application of this method for functional test of the spinal cord through the assessment of the spinal neurovascular response.
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    Peri-spinal Neurovascular Response Triggered by a Painless Electrical Nerve Stimulation in Patients with Chronic Arterial Hypertension
    (2023) Appelgren, Juan Pablo Gonzalez; Caulier-Cisterna, Raul; Oyarzun, Juan Esteban; Uribe, Sergio; Eblen-Zajjur, Antonio
    PurposeAlterations of the central nervous system are frequent complications in patients with chronic arterial hypertension (AHT). However, functional spinal cord lesions are not often detected in these patients despite diagnostic advances in neuroimaging and electrophysiology. Recently, a new non-invasive functional near infrared spectroscopy (fNIRS) application was developed for assessment of the peri-spinal neurovascular response (NVR) as a functional test of the spinal cord.MethodsThe continuous wave fNIRS technique was applied to detect changes in O(2)Hb concentration during the peri-spinal NVR triggered by non-noxious electrical stimulation of the median nerve at the wrist, and recorded at cervical and thoracic spinal levels using three different stimulation protocols in subjects with AHT treated with losartan (n = 22; 142.14 +/- 133.9 months of disease) and compared to healthy control subjects (n = 37). The body mass index (BMI) and the median nerve conduction velocity (NCV) were also recorded.ResultsThe NVR of patients with AHT showed a significantly lower amplitude (- 70.4%; cervical), longer rise time (+ 22.2%; cervical), and longer duration (+ 28.0%; thoracic) than the control group (p < 0.01). The stimulus intensity-response in the AHT group was - 53.5%, - 55.9%, and - 63% lower in amplitude than the controls (p < 0.05) for the increasing stimulus intensity steps (5; 7.5 and 10 mA, respectively) at the cervical level. Patients with BMI > 30 showed more intense changes. The median NCV was normal for both groups.ConclusionThese data show, for the first time, the difference in peri-spinal NVR between normal subjects and losartan-treated ATH patients, indicating the potential of a non-invasive fNIRS technique to find sensory functional abnormalities of the spinal cord in these patients.